For Mercury, as seen in the first graph, this ratio is similar to that for other terrestrial planets at greater distances from the Sun but significantly higher than that for the Moon, which lost potassium during the giant impact that led to its formation.Particularly high potassium concentrations were observed by MESSENGER's Gamma-Ray Spectrometer at high northern latitudes, as illustrated in the abundance map on the left side of the animation.
MESSENGER has provided multiple lines of evidence that Mercury’s polar regions host water ice.
Shown here is a view looking down on Mercury’s north polar region, with 0° longitude on the bottom of the view and extending to 65°N latitude.
In these global views, the Caloris impact basin is initially in the center, and the colors on the spinning globes represent the ratios by weight of magnesium to silicon and aluminum to silicon.
Silicon is known to be relatively homogenous across the surface, so these maps demonstrate variations in the abundances of magnesium and aluminum, both of which are sensitive to the details of the interior melting that produced the lavas that formed the surface volcanic deposits.
The interaction of the planetary field with the solar wind generates currents in the magnetosphere, which induce external magnetic fields with magnitudes similar to or larger than the planetary field in much of the magnetosphere.
Hollows are shallow, irregular depressions and are a geologic landform discovered by MESSENGER that appears to be unique to Mercury.Mercury’s magnetosphere is highly dynamic because of the planet’s small magnetic field and proximity to the Sun.The interaction of the solar wind with the planetary field generates waves in particles and fields, and reconnection of interplanetary and planetary magnetic field lines and circulation of magnetic flux in the magnetosphere occur 100 times faster than at Earth.Hollows are also some of the brightest and youngest features on Mercury’s surface.The floor of the 32-kilometer-diameter crater Kertesz (centered at 27.36°N, 146.11°E), shown here, is extensively covered with hollows.MESSENGER results have shown that Mercury contracted by as much as 7 km in radius, a number substantially larger than previously believed.